1. Field of the Invention
Embodiments of the present invention generally relate to substrate processing systems used for fabricating flat panel displays, semiconductor wafers, and solar panels. In particular, embodiments of the invention relate to substrate supports used in such processing systems.
2. Description of the Related Art
Flat panel displays encompass a growing number of technologies, such as plasma displays, organic light-emitting diode displays, and liquid crystal displays, to name a few. Liquid crystal displays are commonly used for active matrix displays such as computer and television monitors, digital cameras, and an increasing number of other devices. Generally, liquid crystal displays comprise two glass plates having a layer of liquid crystal materials sandwiched therebetween. At least one of the glass plates includes at least one conductive film disposed thereon that is coupled to a power supply. Power, supplied to the conductive film from the power supply, changes the orientation of the crystal material, creating a pattern such as text or graphics seen on the display. One fabrication process frequently used in the production of active matrix displays is plasma enhanced chemical vapor deposition (PECVD).
Plasma enhanced chemical vapor deposition is generally used to deposit thin films on a substrate such as a semiconductor wafer or flat panel glass substrate. In general, PECVD processing involves positioning a substrate on a temperature controlled, heated substrate support, frequently referred to as a susceptor or heater, disposed in a vacuum chamber, and striking a plasma adjacent to the upper exposed surface of the substrate. The plasma is formed by introducing precursor gas into the vacuum chamber and exciting the gas with an electric field using a radio frequency (RF) source coupled to the chamber. The electric field causes the precursor gas to form reactive species which then react to form a film layer on the substrate. The use of a plasma to energize (i.e., excite) the precursor gas allows film deposition to occur at lower temperatures than would be possible using only a heated substrate support to drive the deposition reactions. Plasma processing is particularly well-suited for the production of a flat panel display since the substrate used is typically large and thermally insulative (e.g., glass) and susceptible to warping and bowing if thermal gradients exist within the substrate.
However, the use of plasma processing for large area substrates which are made of electrically insulating materials (e.g., glass and plastic) can lead to charging effects and, in some cases, arcing which may not observed for smaller size substrates or substrates made of semiconducting or conducting materials. Additionally, certain flat panel display applications may require the use of large area, insulating substrates which require placement of a hole or holes within the substrate prior to processing. The hole or holes may be used to facilitate substrate alignment, fixturing, packaging, or other later processing steps for the substrate. The discontinuity in electrical properties for a substrate surface that contains holes may cause non-uniformity in charging effects and differences in electrical potential which may lead to arcing in a plasma processing environment.
Therefore, there is a need for an improved substrate support that reduces arcing during the processing of substrates.